Double row angular contact bearings have an inboard and an outboard row of axially spaced balls, each of which rides between diagonally opposed pathways formed on coaxial inner and outer races. In the context of a vehicle wheel bearing, the inner and outer races are generally referred to as the spindle and hub respectively. By diagonally opposed, it is meant that the pathways do not cover more that 90 degrees, and are located on opposed quadrants. More specifically, one row of balls rides between a pathway on the spindle that contacts their southwest quadrant and a pathway on the hub that contacts their northeast quadrant, while the other row of balls ride between a northwest quadrant pathway on the hub and a southeast quadrant pathway on the spindle.
It is possible to build such a bearing in which all four pathways are ground integral to the hub and spindle. In that case, the spindle and hub have to be manipulated through some fairly complex relative positions in order to install both rows of balls between them, and there is a limit as to how many balls can be inserted into each row. Such bearings are typically called Conrad assembled, or less than full complement, in reference to the limited number of balls possible. The less than full complement of balls also limits the load capacity of the bearing. Because of the limited load capacity of Conrad assembled bearings, a more common approach is to have only three of the four pathways integrally ground to the hub and spindle. Typically, two pathways, one for each ball row, are integrally ground into the hub, and one pathway is ground into the spindle. The remaining pathway is ground onto a separate structure, often called a separable race ring, which is installed and attached to the spindle last, after the last ball row has been installed. This allows a full complement of balls to be installed into each row, because the separable race ring is out of the way when the last ball row is being installed.
While the load capacity of a separable race ring bearing is not limited the number of balls, it is, as is true for any ball bearing, limited by the diameter of the balls. That is, larger diameter balls, if they could be fitted between the spindle and hub, would provide more load capacity. There are limitations on the ball space available between the hub and spindle, however. The spindle and hub can only be so large overall in order to accommodate and clear the wheels, braking, and suspension system of the automobile. They also have to have a certain minimum radial thickness in order to take the loads they must support. The separable race ring itself has a certain minimum radial thickness, so the space available between it and the integrally ground hub pathway that it faces is even more limited. Generally, the inboard and outboard ball rows of separable race ring wheel bearings are of the same diameter. For an example, see U.S. Pat. No. 4,179,167 to Lura et al, assigned to the assignee of the current invention. If a way could be found to enlarge the diameter of even one of the ball rows, without otherwise increasing the size of or weakening the hub or spindle, load capacity would be improved.